Chromosome Abnormalities Flashcards
What is the human genome made of?
46 chromosomes, 22 autosomal, 2 gender
Summarise how to see chromsomes
1) add sample to culture medium
2) Intubate and add colcemid
3) add hypotonic solution
4) Cells spread on slide and drop with stain
5) Karyotype
How do you tell if cell is interphase or metaphase?
Interphase cells are dark, as chromosomes are uncondensed and invisible
What is an Ideogram used for?
See bands on chromosome following Giemsa staining
Bands from centromere outwards
What are the 3 Numerical chromosomal abnormalities?
1) Trisomy e.g. Downs
2) Monosomy: Lose 1
3) Polyploidy: Whole set of chromosomes increase e.g. 69 total
What are the 4 structural chromosome abnormalities?
1) Translocation: Exchange material
2) Inversion: Reversal
3) Duplication: Gain material
4) Deletion: Material is lost
How are gametes ordered in non-disjunction? (M2)
1 gamete has 2 copies, other has 0, and other 2 have 1
What is Robertsonian translocation?
Alignment occurs at top of chromosome causing 2 chromosomes to be stuck together e.g. 14 and 21
What is Reciprocal Translocation?
Balanced like change of material, half of one chromosome stuck onto the end of another
What is FISH used for?
DNA probes, hybridised directly to chromosome, and detect abnormalities e.g. deletion
What are microarrays used for?
Control and Sample DNA added, compete for same sites, and can tell if loss of patient or control DNA or if balanced
(Microdeletions)
What are constitutional changes? (cytogenetics)
Heritable changes that affect all cells at body, occurring at gametogenesis
What are acquired changes?
Non-heritable changes over lifetime, restricted to malignant tissue
4 roles of cytogenetics?
1) Confirmation of malignancy
2) Prognosis
3) Classification of disease type
4) Monitoring
Possible features of non-random changes?
1) Association with lineage
2) Association with clinical feature
3) Close association with disease sub-type
4) No specific/apparent multiple association
